Spreading depolarization evoked changes in vessel diameter. Representative examples of spreading depolarization-induced changes in the diameter of penetrating arterioles (A), first (B), second (C), or third (D) order capillaries at the pericyte cell body (left) or processes (right). Spreading depolarization was triggered by injection of potassium acetate (KAc, black arrow) and evoked changes in the diameters of all types of vessels. These changes were characterized by an initial small vasoconstriction, phase I (light square), followed by a large vasodilation, phase II (dark square), and long-lasting vasoconstriction, phase III (light square). The traces of diameter changes are normalized to a pre-spreading depolarization baseline. The bottom images show the contour of the vessel walls using intra-vascular FITC-dextran over the recording period. SD = spreading depolarization.